Currently unused conduit entrance opening or knockout opening in electrical boxes, housings and enclosure are plugged by using a metallic closure plug such as disclosed in U.S. Pat. No. 3,358,870 to Larkins. However, such closure plugs have several disadvantages. For example, if such a metallic closure plug is utilized with a non-metallic box, then most codes require a bonding jumper to be used for electrically grounding the closure plug. In addition, closure plugs such as those disclosed in the Larkins patent does not provide a weather tight seal sufficient to resist moderate water immersion and a "hose down" from a spray of water. Accordingly, such closure plugs are not suitable for exterior use.
Another closure plug currently being used is the Myers' closure plug which is a two piece, metallic closure plug with a rubber gasket. While the Myers' closure plug overcomes the sealing problem of the closure plug disclosed in the Larkins patent, it still requires a bonding jumper for grounding the closure plug. Accordingly, the Myers' closure plug is time consuming to install on non-metallic enclosure since the Myers' closure plug, like other metallic closure plugs, must be grounded.
Other examples of closure plugs or a coupling for conduits, which are coupled to a knockout opening of an enclosure, are disclosed in French Patent 1,529,492 to Arlati, and in the following U.S. Pat. Nos. 1,491,325 to Thomas, Jr.; 3,072,287 to Sampson; 3,104,120 to Myers; 3,200,366 to Stuart; 3,902,625 to Schmidhuber; and 4,900,068 to Law. However, these closure plugs are often difficult to assembly and disassemble as necessary.
In view of the above, it is apparent that a need exists for a closure plug which does not require grounding when used with a non-metallic enclosure and which is inexpensive to manufacture. This invention addresses this need in the art, along with other needs which will become apparent to those skilled in the art once given this disclosure.